Scroll machines are becoming more and more popular for use as compressors in refrigeration systems as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit with respect to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided which operates to drive the scroll members via a suitable drive shaft.
As the popularity of scroll machines increase, the developers of these scroll machines continue to adapt and redesign the machines for compression systems outside the traditional refrigeration systems. Additional applications for scroll machines include helium compression for cryogenic applications, air compressors, natural gas compressors and the like. The present invention is directed towards a scroll machine which has been designed specifically for the compression of natural gas and/or LP gas.
The cyclic compression of natural gas presents very unique problems with respect to compressor design because of the high temperatures encountered during the compression process. The temperature rise of natural gas during the compression process can be more than twice the temperature rise encountered with the use of a conventional refrigerant. In order to prevent possible damage to the scroll machine from these high temperatures, it is necessary to provide additional cooling for the scroll machine.
The present invention comprises a scroll compressor which is specifically adapted for use in the compression of natural gas. The scroll compressor includes the conventional low pressure oil sump in the suction pressure zone of the compressor as well as a second high pressure oil sump located in the discharge pressure zone. An internal oil cooler is located within the low pressure oil sump. Oil from the low pressure oil sump is circulated to the bearings and other movable components of the compressor in a manner similar to that of conventional scroll compressors. A portion of the oil used to lubricate these moving components is pumped by a rotating component onto the windings of the electric motor to aid in cooling the motor. The oil in the high pressure oil sump is routed through an external heat exchanger for cooling and then is routed through the internal oil cooler located in the low pressure oil sump. From the internal oil cooler, the oil is injected into the compression pockets to aid in the cooling of the compressor as well as to assist in the sealing and lubrication of the intermeshed scroll wraps. An internal oil separator is provided in the discharge chamber to remove at least a portion of the injected oil from the compressed gas and replenish the high pressure oil sump. An oil overflow orifice prevents excessive accumulation of oil in the high pressure oil sump. A second external oil separator is associated with the external heat exchanger in order to remove additional oil from the natural gas to provide as close as possible for an oil free pressurized natural gas supply.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.